1. Field of the Invention
This invention relates to a deep fat fried expanded snack made from a moist dough formed into at least two relatively thin strands and arranged so that the strands are in contact along the long dimension of the snack during frying. This permits expansion of the snack during frying without distorting the shape of the snack.
2. Description of the Prior Art
Many well known shelf-stable snack foods are produced by frying thin pieces of raw vegetables such as potatoes, or by frying shaped pieces of a potato-based or cereal-based dough to a moisture content of about 2%. Raw potatoes are cut into thin slices or narrow sticks known as shoestrings, washed to remove surface starch, and fried for about two to four minutes to produce the familiar potato chip or shoestring potato snacks.
Partially cooked, soaked kernels of corn are ground to form a dough which is forced by hydraulic pressure through a series of narrow openings, and then cut to convenient lengths and fried to form corn chips, as described in Doolin U.S. Pat. No. 2,002,053 and Brown U.S. Pat. No. 3,278,311, et al. Alternately, the ground corn is sheeted between rollers, cut into pieces, baked to reduce the moisture content, and fried, as described in Anderson U.S. Pat. No. 2,905,559, et al.
Potato based doughs used for making snack products by similar methods include methods for making fabricated potato chips described in Succo U.S. Pat. No. 3,519,432, et al, and Liepa U.S. Pat. No. 3,608,474. Willard U.S. Pat. Nos. 3,997,684 and 3,886,291 describe a process in which a dough is formed from cooked potato solids and a raw starch. The dough can be extruded or sheeted and directly fried. The composition of the dough is adjusted so that the extruded products expand during frying from about 1.6 to 3.0 times the extruder die opening. The sheeted products expand during frying from about 1.6 to 4.5 times the opening between the sheeter rolls.
As for the dimensions of the fried products produced from these processes, the finished snack is relatively wide compared to its thickness. For example, conventional corn chips can be extruded through a die slot having a thickness of about 0.050 inch and a width of about 0.50 in. to 1.25 inch. Potato rings can be extruded through a die with a 0.045 inch opening measured radially with an outer diameter of 0.625 inch, i.e., a circumference of about 2.0 inches.
Fried snack products formed as an elongated strand are particularly desirable to consumers. Shoestring potatoes can be conveniently formed from raw potatoes; and since the internal cell structure of the raw potato is maintained throughout frying, the product does not distort or curl during frying. Pretzel dough is extruded as a round, thin strand and then baked on a supporting oven conveyer to produce pretzel sticks, which do not distort or curl during baking. However, attempts to produce an elongated strand-like fried snack from a moist dough have generally not been successful, insofar as avoiding undesired distortion during frying is concerned. Because of the relative narrow cross-sectional dimensions of strands compared to their length, the products tend to curve or curl and tangle together, resulting in unattractive random shapes when they are removed from the hot frying fat. Another problem we have discovered is that narrow, elongated strands made from many dough compositions tend to form irregular protuberances during frying due to the internal pressure generated by escaping steam at frying temperatures. It appears that the outer surfaces of the fried strands become impervious to the escape of steam during the initial moments of frying. Later, as heat is transferred to the interior portion of the strand, the increased vapor pressure of the remaining water creates intense internal pressure. This causes the side walls of the strand to bulge and deform and, in some cases, to crack open or explode. We have noted that this condition is particularly prevalent when the ingredients of the dough contain a significant quantity of an ungelatinized or raw starch. Similar ingredients that exhibit a rapid increase in viscosity upon heating in the presence of water also can create explosions in the fryer.
In British patent No. 1,109,930 to Southern, round "straws" are produced from a fresh potato dough by extruding the dough vertically through a horizontal die plate with 0.125 inch diameter holes. These straws are cut into 2-inch lengths and fried from four to five minutes at a temperature of 300.degree.-350.degree. F. without any appreciable increase in diameter taking place during frying. Care is taken during extrusion that the straws do not touch or stick together. The straws curl excessively upon frying. The finished product contains about 50% fat, requiring centrifuging to reduce the fat content to a more desirable 30%.
In British patent No. 1,187,762 to Bolton et al, 5 mm. square sticks are extruded from a dough comprising cooked potato solids, a starch and a filler. The potato sticks are fried eleven minutes at an undisclosed temperature. The fried products require centrifuging to reduce the fat content from 45% to about 25%. We have found that the dough sticks formed by the mixtures described in this patent create dangerous explosions during deep fat frying.
M. F. Peden, Jr. U.S. Pat. No. 3,190,755 describes a process for making a strand-like snack product in which a cooked dough is extruded to form one-eighth inch diameter strands. These strands are case-hardened and rolled flat, causing the hardened outer surface to shatter. The strands are then dried to reduce their moisture content to about 10% before frying to produce an expanded product with a rippled surface upon frying.
Dexter U.S. Pat. No. 3,966,983, et al. describes a frying process to eliminate distortion of thin formed pieces of dough such as simulated shoestring potatoes. The thin dough pieces are pre-cooked with heated oil while the dough pieces are supported on a screen-like conveyor. The pieces are then fried conventionally after they have stiffened from the oil treatment. The pieces so treated are relatively thin and flat, having been cut from a rolled dough sheet. While the treatment is said to reduce the amount of distortion during frying, the equipment is complex and expensive, and the spraying of hot frying oil can cause rapid buildup of free fatty acids.
Elongated, square-sided potato products have been made from doughs consisting essentially of rehydrated dried potatoes to form fabricated French fried potatoes, for example. Processes for making the dough for such products are described in Fritzberg U.S. Pat. No. 3,282,704; Willard U.S. Pat. No. 3,399,062, et al.; Citti U.S. Pat. No. 4,198,437, et al.; and Shatila U.S. Pat. No. 3,968,265. Apparatus for producing French fries is described in Shatila U.S. Pat. No. 4,056,345, et al and Ilines U.S. Pat. No. 3,645,748. The dough compositions used in these processes generally contain a higher level of water than the processes for making the snack products of this invention. In French fry processing, frying is continued only long enough to form a crisp brown skin on the surface of the finished product, whereas in producing the fried snacks of this invention water removal is nearly complete.
Thus, it is desirable to produce a strand-like expanded fried snack by frying a moist dough, without intermediate treatment following forming of the dough piece, so that the shape of the snack des not distort during frying. Undesired distortion includes curling of the strand-like product, formation of undesired protuberances on the finished product, explosion of the product in the fryer, or agglomeration of the fried dough pieces in the fryer.